1. Technical Field
The present invention relates generally to ion implantation, and more particularly, to a system, method and program product for determining an ion beam contamination.
2. Related Art
Ion implantation is a standard technique for introducing conductivity altering impurities into, or doping, semiconductor wafers. A typical ion implantation process uses an energetic ion beam to introduce impurities (ions) into semiconductor wafers. During ion implantation, when a source feed material is energized to form an ion beam, species of different chemical elements may be energized to generate ions having the same or very similar mass/charge ratio as the expected ion, which may be difficult to separate from the expected ions in the ion beam in a commercially productive manner. As a consequence, the contaminant ions will also be implanted into the semiconductor wafers, which may cause serious divergences in the desired parameters of semiconductor devices made from the wafers, and lead to scrap.
To avoid an implantation of a contaminated ion beam, measurements need to be taken to determine the existence and/or seriousness (i.e., the relative amount of a contaminant ion) of an ion beam contamination. However, if the mass/charge ratio of a contaminant ion is very close to that of an expected ion, it is difficult to detect the existence of the contaminant ion directly because a peak of the contaminant ion and a peak of the expected ion may be difficult to separate in a mass spectrum graph. As such, there is a need to determine the existence and/or seriousness of an ion beam contamination indirectly. There is also a need to determine whether an ion implantation system has a capacity to filter out contaminant ions sufficiently to make a potential contamination meet a preset threshold.